Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Broken seesaw warms North


Wetter winters could be forecast months ahead.
© ImageSource

American Geophysical Society Meeting, San Francisco, December 2001

Pressure system secrets could help long range forecasts.

The rise in levels of greenhouse gases has halted an oscillation of air pressures over the Arctic, bringing warmer, wetter winters to Northern Europe, Siberia and Alaska. The shift could get worse with increasing CO2 emissions, delegates heard this week at the American Geophysical Union meeting in San Francisco, California.

The trend is unlikely to have a natural cause, Nathan Gillett, a climate modeller at the University of Oxford in the UK, told the conference. "It is consistent with most climate models’ response to greenhouse gases," he added.

But the cloudy winter skies over Europe may have a silver lining. Identifying the effects of the Arctic oscillation (AO) could one day enable researchers to forecast aspects of northern hemisphere weather months, even seasons ahead of time.

Like El Nino, the AO is a variation in atmospheric pressure. It seesaws between Iceland at one end and Spain and Portugal at the other. The AO’s negative phase brings higher-than-normal pressure to the polar region and lower pressure to Eurasia and North America. The positive phase brings the opposite: warmer, wetter weather to northern regions and dryer conditions to lower latitudes.

Scientists used to think that the AO was completely random. But in 1995 James Hurrell of the National Center for Atmospheric Research in Boulder, Colorado, showed that it actually follows a 10-year cycle and that since the 1980s the seesaw has been stuck in its positive phase1. "This has an impact on winter surface temperatures," says Hurrell.

Recent estimates suggest that the skewed AO may account for half of the warmer winter episodes and rainfall in northern Atlantic areas such as Scotland.

Working with the computer models used to forecast Britain’s weather, Gillett calculated the impact of a doubling of atmospheric CO2 levels (expected to happen by about 2040) on the AO’s intensity. He found that the additional CO2 would keep the AO in its positive phase and strengthen its effects.

Most experts agree that the skewed AO is probably caused by greenhouse gases, according to climatologist John Wallace at the University of Washington in Seattle. Although he cautions that climate models are never perfect.

High cycle

What happens to the AO in the absence of man-made perturbations, on the other hand, is open to debate. One suggestion is that increasing tropical ocean temperatures cause the phenomenon. Another proposes that long-term cycles high in the stratosphere, six to thirty miles above the Earth, are driving it.

New evidence presented at the meeting by Mark Baldwin, of Northwest Research Associates in Bellevue, Washington, suggests that fluctuations in the stratosphere’s thickness are linked to the AO.

Although the effects of the stratosphere will still be amplified by an increase in greenhouse gases, the finding is otherwise good news, says Wallace, because the frequency of the waves are known. "These stratosphere waves could make 60-day forecasts possible," he says.

What’s more, longer-term fluctuations in tropical Atlantic temperature contribute to the power of stratospheric waves, so it should be possible to predict weather seasons in advance, says Wallace. "One day we might be predicting the likelihood of a certain number of cold snaps in the coming year," he says.


  1. Hurrell, J. W. Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation. Science, 269, 676 - 679, (1995).

TOM CLARKE | © Nature News Service
Further information:

More articles from Earth Sciences:

nachricht Wandering greenhouse gas
16.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Unique Insights into the Antarctic Ice Shelf System
14.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>